Signal capture devices such as digital, still and video cameras produce raw digital signals (images, video, sound) that contain noise. The noise can result from a device's image sensor, read channel, etc. The noise in images, for example, can be exacerbated by post-processing such as demosaicing, tone mapping, and color correction.
Post-processing algorithms such as denoising, sharpening and equalization should be able to distinguish between noise and signal features. For example, if sharpening cannot distinguish noise from image features, it will amplify noise and artifacts. If denoising cannot distinguish between noise and image features, it will oversmooth features such as edges and texture.